Powder metallurgy method for producing non-molybdenum segregated article

ABSTRACT

A powder metallurgy method for producing a non-molybdenum-segregated article is disclosed. The method includes use of a Ni—Mo—Cr powder that has a composition in which Ni is the base element and the Mo and Cr are alloy elements. The composition comprises, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder. The Ni—Mo—Cr powder is inserted into a hermetic chamber of a canister, followed by evacuating the hermetic chamber. The canister with the Ni—Mo—Cr powder in the hermetic chamber is then subjected to a hot isostatic pressing process that includes heating the canister and the Ni—Mo—Cr powder and applying isostatic pressure to the canister. The heating and the isostatic pressure causes fusion and consolidation of the Ni—Mo—Cr powder to form a solid article. The Mo remains dispersed such that the solid article is non-molybdenum-segregated. The canister is then removed from the solid article.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 62/747,844 filed Oct. 19, 2018.

BACKGROUND

Low coefficient of thermal expansion compositions of Ni alloys may include Ni as the base metal and Mo and Cr as alloy elements. In particular, the Mo is often present in relatively high alloy amounts. The alloy is processed using a cast-wrought process to produce end-use components. First, the alloy is produced in a vacuum induction melting process and then refined into ingots using electro-slag remelting or vacuum arc remelting. The ingots are then pressed and forged to form billets. The billets may be cut and subsequently forged into the end-use components.

SUMMARY

A powder metallurgy method for producing a non-molybdenum-segregated article according to an example of the present disclosure includes a Ni—Mo—Cr powder that has a composition in which Ni is the base element and the Mo and the Cr are alloy elements. The composition includes, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder. The Ni—Mo—Cr powder is inserted into a hermetic chamber of a canister, followed by evacuating the hermetic chamber subjecting the canister with the Ni—Mo—Cr powder in the hermetic chamber to a hot isostatic pressing process that includes heating the canister and the Ni—Mo—Cr powder and applying isostatic pressure to the canister. The heating and the isostatic pressure causes fusion and consolidation of the Ni—Mo—Cr powder to form a solid article. The Mo remains dispersed such that the solid article is non-molybdenum-segregated and removes the canister from the solid article.

In a further embodiment of any of the foregoing embodiments, the composition comprises, by weight, 24% to 26% of the Mo.

In a further embodiment of any of the foregoing embodiments, the composition comprises, by weight, 7% to 9% of the Cr.

A further embodiment of any of the foregoing embodiments includes forming one or more end-use components from the solid article.

A further embodiment of any of the foregoing embodiments includes forming the Ni—Mo—Cr powder.

A powder metallurgy method for producing a non-molybdenum-segregated article according to an example of the present disclosure includes forming a Ni—Mo—Cr powder that has a composition in which Ni is the base element and the Mo and the Cr are alloy elements. The composition includes, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder. The Ni—Mo—Cr powder is inserted into a hermetic chamber of a canister, followed by evacuating the hermetic chamber, subjecting the canister with the Ni—Mo—Cr powder in the hermetic chamber to a hot isostatic pressing process that includes heating the canister and the Ni—Mo—Cr powder and applying isostatic pressure to the canister. The heating and the isostatic pressure causes fusion and consolidation of the Ni—Mo—Cr powder to form a solid article. The Mo remains dispersed such that the solid article is non-molybdenum-segregated. The canister is then removed from the solid article, and one or more end-use components are formed from the solid workpiece.

In a further embodiment of any of the foregoing embodiments, the composition comprises, by weight, 24% to 26% of the Mo.

In a further embodiment of any of the foregoing embodiments, the composition comprises, by weight, 7% to 9% of the Cr.

In a further embodiment of any of the foregoing embodiments, the forming includes extruding the solid article.

In a further embodiment of any of the foregoing embodiments, the forming includes cutting the solid article into pieces.

In a further embodiment of any of the foregoing embodiments, the forming includes forging the solid article.

In a further embodiment of any of the foregoing embodiments, the forming includes extruding the solid article into a billet, cutting the billet into pieces, and forging the pieces.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

FIG. 1 depicts a powder metallurgy method for producing a non-molybdenum-segregated article.

FIG. 2 depicts another example of a powder metallurgy method for producing a non-molybdenum-segregated article.

DETAILED DESCRIPTION

In low coefficient of thermal expansion compositions of Ni alloys, the Mo is often present in relatively high alloy amounts. Molybdenum in high amounts, however, tends to segregate in high volume melts. As a result, it is difficult to employ such alloys in components because use of fabrication techniques that employ high volume melts results in Mo-segregation that leads to non-uniform properties and/or properties that are below requirements.

FIG. 1 schematically illustrates a powder metallurgy method 20 that can be used to address segregation and produce a non-Mo-segregated article. The method 20 includes use of a Ni—Mo—Cr powder 22 that has a composition in which Ni is the base element and the Mo and the Cr are alloy elements. The composition has, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder, as shown in the inset view of a representative particle 22 a of the powder 22. In further examples, the composition has, by weight, 24% to 26% of the Mo and 7% to 9% of the Cr. The composition may also have up to 0.03% C, up to 0.80 Mn, up to 0.80 Si, up to 0.03% P, up to 0.015% S, up to 0.50 Al, up to 0.006 B, up to 2.00% Fe, and up to 0.50 Cu. In additional examples, the composition has only the elements in the amounts prescribed above, and all other elements are assumed to affect the basic and material properties of the composition for its use as a low coefficient of thermal expansion alloy, particularly in gas turbine engine applications.

The powder 22 is inserted, as shown at 24, into a canister 26. The canister 26 has a hermetic chamber 26 a. For instance, the canister 26 may include metal walls that are welded or otherwise bonded together in an airtight manner to form the hermetic chamber 26 a. The canister 26 may be provided with a port 26 b for accessing the hermetic chamber 26 a. The powder 22 may be inserted through the port 26 b into the hermetic chamber 26 a.

The hermetic chamber 26 a is then evacuated, as represented at 28. As an example, a pump may be used to draw air or other gases out of the hermetic chamber 26 a. The evacuation process may include flushing the hermetic chamber 26 a with one or more inert gases, such as argon, helium, or mixtures thereof. The port 26 b may subsequently be sealed off, such as by welding or the like.

The canister 26 with the metallic alloy powder 22 is then subjected at 30 to a hot isostatic pressing (“HIP”) process. The HIP process includes heating the canister 26 and the metallic alloy powder 22 and applying isostatic pressure to the canister 26. The heating causes sintering and fusion of the powder 22, while the pressure deforms the canister 26 and thereby compresses the powder 22 to consolidate the powder as it fuses. The time, temperature, and pressure used may be varied in order to obtain a desired degree of consolidation and sintering. As an example, the HIP process is conducted at a pressure of 25 kilopounds per square inch, a temperature of approximately 2000° F., for a time of approximately 4 hours. The fusion and consolidation of the powder 22 forms a solid article 32. The Mo, which was dispersed in the powder 22, remains dispersed such that the solid article 32 is non-molybdenum-segregated. For instance, when in a high volume melt, the Mo can migrate or settle out and thereby produce regions that have high concentration of Mo and other regions that have low concentration of Mo. However, since sintering does not rely on entirely or substantially entirely melting, the Mo in the powder 22 remains well dispersed in the solid article 32.

As shown at 34, the canister 26 is subsequently removed from the solid article 32. As an example, the canister 26 can be removed by machining.

The powder metallurgy method 20 is not limited to the above steps or actions. For example, as also shown at 40, the method 20 may additionally include forming the powder 22. For instance, the forming may include atomization of the molten alloy. The molten alloy can be well-mixed or agitated such that the Mo is well dispersed when it is atomized Each atomized droplet thus has well-dispersed Mo such that the powder 22 nominally has a good dispersion of the Mo.

The method 20 may also include extruding the solid article 32, as indicated at 42. For instance, the solid article 32 is pushed through a die that reduces the cross-section of the solid article 32 to produce a billet 44. As shown at 46, the billet 44 may then be cut into multiple pieces, which may also be known as stocks, blanks, mults, or slugs that are used as inputs into further processes. The stocks, blanks, mults, or slugs may then be forged, as indicated at 48, to produce one or more end-use components 50 (e.g., rotor disks). As will be appreciated, depending on the shape of the solid article 32, the extruding and/or cutting may not be necessary and the solid article 32 may be directly forged at 48 after removal of the canister in method 20.

In another alternative shown in FIG. 2, the method 120 is similar to the method 20 but excludes the extruding, cutting, and forging. In this example, the canister 26 with the metallic alloy powder 22 is subjected at 130 to the HIP process as described above. However, rather than forming the solid article 32 as an intermediate workpiece, the end-use component 150 is formed directly from the HIP process. Such direct HIP process may be employed, for example, in applications where components are not life limited.

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims. 

What is claimed is:
 1. A powder metallurgy method for producing a non-molybdenum-segregated article, the method comprising: a Ni—Mo—Cr powder that has a composition in which Ni is the base element and the Mo and the Cr are alloy elements, the composition comprises, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder; inserting the Ni—Mo—Cr powder into a hermetic chamber of a canister, followed by evacuating the hermetic chamber; subjecting the canister with the Ni—Mo—Cr powder in the hermetic chamber to a hot isostatic pressing process that includes heating the canister and the Ni—Mo—Cr powder and applying isostatic pressure to the canister, the heating and the isostatic pressure causing fusion and consolidation of the Ni—Mo—Cr powder to form a solid article, the Mo remaining dispersed such that the solid article is non-molybdenum-segregated; and removing the canister from the solid article.
 2. The method as recited in claim 1, wherein the composition comprises, by weight, 24% to 26% of the Mo.
 3. The method as recited in claim 2, wherein the composition comprises, by weight, 7% to 9% of the Cr.
 4. The method as recited in claim 1, further comprising forming one or more end-use components from the solid article.
 5. The method as recited in claim 1, further comprising forming the Ni—Mo—Cr powder.
 6. An end-use component formed from the solid article produced by the method as recited in any of the prior claims.
 7. A powder metallurgy method for producing a non-molybdenum-segregated article, the method comprising: forming a Ni—Mo—Cr powder that has a composition in which Ni is the base element and the Mo and the Cr are alloy elements, the composition comprises, by weight, at least 20% of the Mo, and the Mo is dispersed in the Ni—Mo—Cr powder; inserting the Ni—Mo—Cr powder into a hermetic chamber of a canister, followed by evacuating the hermetic chamber; subjecting the canister with the Ni—Mo—Cr powder in the hermetic chamber to a hot isostatic pressing process that includes heating the canister and the Ni—Mo—Cr powder and applying isostatic pressure to the canister, the heating and the isostatic pressure causing fusion and consolidation of the Ni—Mo—Cr powder to form a solid article, the Mo remaining dispersed such that the solid article is non-molybdenum-segregated; removing the canister from the solid article; and forming one or more end-use components from the solid workpiece.
 8. The method as recited in claim 7, wherein the composition comprises, by weight, 24% to 26% of the Mo.
 9. The method as recited in claim 8, wherein the composition comprises, by weight, 7% to 9% of the Cr.
 10. The method as recited in claim 7, wherein the forming includes extruding the solid article.
 11. The method as recited in claim 7, wherein the forming includes cutting the solid article into pieces.
 12. The method as recited in claim 7, wherein the forming includes forging the solid article.
 13. The method as recited in claim 7, wherein the forming includes extruding the solid article into a billet, cutting the billet into pieces, and forging the pieces. 